Crosslinking process

ABSTRACT

THE CURING OF ALPHA-OLEFINS AND OF ALPHA-OLEFIN COPOLYMERS WITH QUINONE DIOXIME ESTERS IS ACCELERATED BY THE ADDITION OF A LEWIS ACID. THE CURING TEMPERATURE IS LOWERED STILL FURTHER BY THE ADDITION OF A POLAR ORGANIC MEMBER OF THE GROUP CONSISTING OF CARBOXYLIC ACIDS, PHOSPHORIC ACID, BORIC ACID, AND ESTERS THEREOF, AND FILLERS SUCH AS CARBON BLACK AND/OR OTHER CONVENTIONAL ADDITIVES MAY BE INCLUDED.

Aug. 1o, 1911 c, KEHR am CROSSLINKING PROCESS Re. :ms

5 Shoots-Shut 1 Original Filed Oct. 24, 1962 e m n o. S w. Kmm QN SN SwQQ g B on L w A V gwkovo Mm Q tu svnlbzk .FSE 2 ou. n n Q m m tu QSI SnEen nu .itmcqw J .w m EN ESME .EBSQ .ERE Qnluvdgov n.,

QN e f 9 H 90 o QQ Nmnwmxa .Nk b" .Qx klm .KQ xbb lsQbmQ Wkvtb .kbmkxk QN QQN KQ kbmllm c. L. KEHR ErAL Re. 27,158

cRossLINkING PROCESS Aug. 1o, 1971 Sheets-Shoot :j

Original Filed Oct. 24, 1962 Q QON QQ QQ QQ im ESQ ooh ,..SGQQ o... o

Clifton L. Kehr James L. Gul/m klm N WQDK Aug. 10, if C VL, KEHR ETAL vR0. 21,158

GROSSLNKINQ POQSS '5 shutp-Bhut s Original Filed Oct. 241,; 1962 QQ QQQk` QQ QQ QQ QQ emu .25m Sis .2352. 323s 3 *EN sa. und waas! Nn e b Kfm@om ruao* L rw Lm QMSvw/ ../,ewv A wmf.

x s u .om MWQQQ n U.S. Cl. 260-41.5

United States Patent O 27,158 CROSSLINKING PROCESS Clifton L. Kehr,Silver Spring, and James L. Guthrie, Ashton, Md., assignors to W. R.Grace & Co., New York, N.Y.

Original No. 3,226,356, dated Dec. 28, 1965, Ser. No. 232,771, Oct. 24,1962. Application for reissue Nov. 28, 1969, Ser. No. 888,173

Int. Cl. C08d 11/00; C081. 3/02, 45/08 16 Claims Matter enclosed inheavy brackets appears in the original patent but forms no part of thisreissue specilication; matter printed in italics indicates the additionsmade by reissue.

ABSTRACT F THE DISCLOSURE The curing of alpha-olefins and ofalpha-olefin copolymers with quinone dioxime esters is accelerated bythe addition of a Lewis acid. The caring temperature is lowered stillfarther by the addition to the caring system of a synergistic agentconsisting of a polar organic member of the group consisting ofcarboxylic acids, phosphoric acid, boric acid, and esters thereof, andfillers such as carbon black and/ or other conventional additives may beincluded.

This invention relates to crosslinked polymers derived from a-olens andcopolymers containing same and methods of preparing same. Moreparticularly this invention is concerned with crosslinking polymersderived from aoletins and copolymers containing same at temperaturesabove their processing temperature at a rapid rate with a novelcross-linking system.

In the eld of polymers derived from a-olens, there is a continuingsearch for new and better crosslinking agents. Of special interest arethose which are unreactive at processing and compounding temperatures,but which can be triggered in some manner after the polymer compound isprocessed into its nal shape by molding, extruding or the like.

Thus in the polyolen art, there has been a long felt want forcrosslinking agents which not only crosslink at operable and economicaltemperatures above the processing temperature of the polymer orcopolymer but also crosslink at a rapid rate at said temperature so asto require a very short cure time.

In a copending application having Serial Number 168,025, filed I an. 18,1962 and assigned to the same assignee, it has been discovered thatesters, both mono and di, of quinone dioxime are excellent crosslinkingagents for normally solid polyolelns. The only drawback, however, isthat the curing temperature is necessarily high, e.g. for polypropylenea temperature of 225 C. is necessary to obtain a suciently high gelcontent in the polymer. Thus although the esters of quinone dioxime haveexcellent scotch (pre-cure) resistance at the high temperatures (U-200C.), such exceptional stability is not required, in fact, is not desiredin curing certain polymers derived from a-olens and copolymerscontaining same.

For example a copolymer derived from a-olens which has recently enteredthe market on a commercial scale is the poly nt-olefin copolymer,ethylene/propylene rubber (EPR). Because of low monomer cost, EPRpromises to be the rubber industrys lowest priced elastomer. Due to itsessentially nil double bond content, EPR is outstanding (relative toother vulcanizable elastomers) in its resistance to degradation byoxygen and ozone. For the same reason, however, EPR is rather diicult tovulcanize. For example, ethylene/ propylene rubber cannot be vulcanizedWith standard sulfur/accelerator recipes. Comp i ICC mercialmanufacturers of EPR currently recommend a dicumyl peroxidevulcanization recipe (usually modified with a small quantity of sulfurto minimize degradation of the EPR during the cure). This system,although operable, has the following disadvantages: (l) obnoxious odorsfrom a combination of acetophenone and mercaptan-like sulfur compounds,(2) high temperature/time curing cycles which are rather inflexiblesince there are no known accelerators or retarders for peroxides, and(3) the adhesion of the cured EPR to tire cords is extremely poor.

One commercial approach taken to overcome the disadvantages of EPR hasbeen the development of a sulfur-curable hydrocarbon rubber based onethylene and propylene. This product contains, beside ethylene andpropylene, a third monomer unit derived from a nonconjugated diene andis sold under the trade name Nordel by E. `I. du Pont de Nemours andCo., Inc. The resulting terpolymer after polymerization contains acontrolled degree of unsaturation which as in the case of butyl rubber,serves as curing sites for vulcanization with standard sulfur-containingaccelerators. Although the odor problem is less critical by the use ofthis terpolymer, the curing rate is still sluggish requiring a cure ofapproximately 30 minutes at 160 C. By ordinary rubber industrystandards, these conditions are too long and too high to be economicalfor general usage, especially in the tire industry.

The rubber tire industry generally desires a standard curing temperaturerange of 13G-150 C. for a period of no more than 10-20 minutes. Atprocessing temperatures below said range, the crosslinking orvulcanizing agents employed must be relatively non-scorchy but whenheated within said range the crosslinking agents must be able to rapidlycure the polymer. To employ crosslinking agents which cure attemperatures above the aforementioned range would be uneconomical forthe ber tire industry as it would necessitate in many instances theintroduction of higher pressure steam generating units and a redesign ofpresent equipment to withstand the higher steam pressure.

Therefore, one object of this invention is to provide a novelcrosslinking system which effects curing of polymers derived froma-olens and copolymers containing same, especially amorphous copolymerssuch as EPR, in the range 150 C. at an operable rate without scorching(pre-curing during processing). In fact, this novel crosslinking systemis so versatile in the case ofIEP-R that one can, by proper choice ofcuring agent and accelerator, formulate compositions so that rapid andcomplete crosslinking will occur at any predesired temperature rangingbetween the limits of 130 C. and 215 C. In addition, temperatures can beselected readily so that curing cycles of extremely short duration, c g.2 minutes or less, can be achieved.

Still another object of the present invention is to provide a class ofsynergistic agents which when combined with the crosslinking agents andaccelerators therefor of this invention lower the curing temperaturestill further.

Other objects and advantages of this invention will become apparent froma reading hereinafter.

Summarily this invention relates to curing polymers derived from a-olensby admixing said polymers ywith a curing agent of the general formula,

As used herein the term a-olen means a hydrocaraon monomer whichcontains a single terminally unsatu- 'ated grouping of the formula-CH=CH2.

As used herein the term polymers derived from a-oleins includes coandterpolymers wherein at least 50 nole percent of the polymer is derivedfrom a-olefins as lerein defined. Thus, polymers derived from a-oleiinsvould include, but are expressly not limited to, polyethylene,polypropylene, ethylene/ propylene copolymers, ethylne/butylenecopolymers, ethylene/propylene/diene terrolymers, and ethylene/ vinylacetate copolymers, said atter two containing at least 50 mole percentof the poly t-olens. The polymers derived from a-olefins as meant lereinwould also include polymers derived from a-oleins which had been furtherprocessed such as having been :hlorosulfonated, e.g. chlorosulfonatedpolyethylene as decribed in U.S. 2,212,786.

In this invention the term acyloxy means n which R is an aliphaticgroup.

substituents may be present in the ortho, meta and ara positions of thebenzene ring of the benzoate group f the curing agent. substituents suchas halogens, alkyl groups, alkoxy groups, nitro groups, etc. areoperable. Xlso operable are other aromatic .groups besides the enzenoidring. For example, quinone dioxime esters of or 2-naphthoic acidfunction as well as similar esters f =benzoic acid but in most cases aremore costly. The luinone dioxime esters of the aliphatic carboxylicacids, .e., the aliphatic acyloxy-substituted quinone dioximes are tlsooperable in substituted form. Substituents such as he halogens have beenemployed as will be shown lereinafter.

In the present invention the term Lewis acid means L substance which canfill the valence shell of one of its Ltoms with an unshared pair ofelectrons from another nolecule. Examples of Lewis acids include but arenot imited to A1013, FeCl3, SnCl4, ZnClZ, TiCl4, CrCl3, JC14, A1Br3,HgCl2, BF3 and the like. Also included in his definition are mixtures ofcompounds which, when )rought together in the polymeric compositionunder ztandard conditions of processing interact with each other o-generate the Lewis acid in situ. Alsoincluded in the lefinition ofLewis acids herein are Lewis acid coordilation compounds which prior toaddition to the rubber :ompound have their maximum coordination numbersatisfied, but which in the course of compounding and :uring interactwith the curing agent. Examples of this atter type of Lewis acidcoordination complexes are illusrated by but not limited to ferrcacetylacetonate, aluninum aoetylacetonate, boron fluoride, n-butyletherate, :inc chloride: 2,2-dithiobisbenzothiazole complex and the ike.The addition of said Lewis acid accelerators to the :ystem causesoptimum curing to occur (as shown by gel content of the polymer), attemperatures below the )ptimum curing temperature of the esters ofquinone lioxime per se as will be shown hereinafter.

In addition it has been found that the optimum curing emperature of thenovel curing agents and accelerators )f the instant invention can, ifdesired, be lowered still urther by adding to the system a synergisticagent con- `isting of a polar organic member of the group consisting lfcarboxylic acids, phosphoric acid, boric acid, and :sters thereof.Examples of synergistic agents operable n the instant invention include,but are not limited to, 1-butyl stearate, tributyl citrate, tributyrin,tributyl phosihate, tributyl borate, stearic acid, and the like.

The amount of crosslinking agent used in this invention s not criticaland can vary over wide limits depending lpon the polymer beingcrosslinked. Amounts of esters )f quinone dioxime crosslinking agent inthe range ).1-30 parts per hundred parts of polymer by weight 4preferably 0.5-20 parts per hundred parts of polymer are employed.

The amount of Lewis acid accelerator used is in the range 0.005211) partby weight per hundred parts of polymer and preferably 0.0l0.5 part onthe same basis. The Lewis acid accelerator may, if desired, be added tothe compounding step as a solution (5-20% by weight) in suitablesolvents, for ease of handling and for uniformity of dispersion. Lowboiling organic solvents such as acetone, isopropanol, ethanol, benzene,and the like are operable. The solvent is boiled olf in the compoundingstep.

The amount of synergistic agent employed herein is in the range 0.1-30parts per hundred parts of polymer by weight and preferably 0.5-3.0parts on the same basis.

The polymer compositions to be cured in accord with the presentinvention may, if desired, include such additives as antioxidants,fillers, pigments, anti-static agents, extending oils, plasticizers,tackifiers and the like within the scope of this invention. Suchadditives are usually but not necessarily added to the polymercomposition by pre-blending prior to or during the compounding step.Operable fillers would include carbon black, clay, silica, alumina,carbonates, oxides, hydroxides, silicates, diatomaceous earth, talc,kaolin, barium sulfate, calcium sulfate, calcium carbonate and the like.The aforesaid additives may be present up to 200 parts or more per partsof polymer by weight and preferably 0.05-100 parts on the same basis.

Although the invention is operable with polymers derived from a-olelinsand copolymers containing same, for ease of explanation and clarity theinvention will, in the main, be explained using ethylene/propylenerubber (EPR) as the polymer to be cured.

The general procedure followed in performing this invention is to form acompound of the desired ingredients ina Bansbury mixer, two-roll mill,Brabender Plastograph and the like at temperatures in the range 25-200C. The compounding temperature is determined by and is in excess of thesoftening point of the polymer but is below the curing temperatureexhibited 'by the crosslinking agent. While milling the polymer aboveits softening point (which for EPR usually would be in the range 25-l20C.), any filter and any synergistic agent are compounded in withcontinued milling. The crosslinking agent is then added followed by theaddition of the Lewis acid accelerator. It is possible to add all theaforementioned components together to the softened polymer but for moreuniform mixing and ease of handling, they are preferably added stepwise.The resulting compound is then processed into its final shape by anextruding or molding step under pressure at temperatures above thesoftening point of the polymer but below the curing temperatureexhibited by the crosslinking agent. This step is followed by heatingthe shaped article to a higher temperature ran-ge, e.g. for EPR atemperature in excess of 130 C. whereat rapid curing of the polymer iseffected. The curing temperature is dependent upon many factors,including (l) the polymer being cured, (2) the actual crosslinking agentand accelerator within the classes disclosed and the amounts thereof,and (3) whether or not a synergistic agent is added. As a ,general rulethe curing temperature employed for optimum curing, i.e. where the stateof cure (percent gel) plateaus out, in the instant invention is from to200 C.

The following examples are set down as an aid in understanding theinvention but are expressly not designed to limit its scope. In theexample, unless otherwise noted, all parts and percentages are by weightper hundred parts of polymer.

Throughout the instant invention the melt indices (MI) were measuredunder the conditions specified in ASTM D-l238-52T, except for isotacticpolypropylene, in which instaance the procedure was modified so that thetest was run at 230 C. instead of 190 C. The densities of the polymerswere measured under the conditions specified in ASTM D-1505-57T. Thepercent gel content of the polymers in the instant invention wasmeasured by refluxing a weighed sample (approximately 0.5 g.) of polymerin a cellulose Soxhlet thimble in a suitable solvent (containing 0.3weight percent 2,6- ditertiary-butyl-4-methyl-phenol commerciallyavailable under the trade name Ionol from Shell Oil Corp. for 24 hours.The insoluble portion of the polymer sample after drying was weighed tocalculate percent gel as follows:

Weight insoluble sample total Weight sample In examples wherein anadditive such as a filler, e.g. carbon black, clay and the like waspresent in the compound the percent rgel content was calculated so as toexclude the inert insoluble additive. Thus as used herein percent gelcontent is based solely on the polymeric hydrocarbon content of thecured polymer. Suitable solvents for the polymer compositions describedherein include heptane, xylene, methylethyl ketone and the like, theonly restriction being that the uncured polymer should be completelysoluble in said solvent under conditions of the extraction procedure.

Mooney viscosity was measured in accord with the conditions specied inASTM D164661.

In all examples, unless otherwise noted, a Brabender percent gel X lperiods ranging from 1 to 15 minutes at various curing temperatures. Thesamples were then removed from the press and cooled in air. Samples ofthe cured specimens were then used to calculate the percent gel contentby the aforementioned solvent extraction method.

Table I shows a comparative study of the accelerating effect of variousLewis acid accelerators and synergistic agents on the crosslinking agentin curing ethylene/propylene rubber (EPR). The compounding was performedina Bra'benider Plastog-raph at 80-110 C. The components of the compoundwere milled together over a period of 10 minutes. Samples of thecompounded EPR were cured by placing them Iin a 6 x 6" x 0.02 mold andpressing them in a platen press for 15 minutes and 625 p.s. i. atvarying cure temperatures. Weighed samples of the cured EPR were thenmeasured for gel content in reuxing n-heptane containing a small amountof an antioxidant for 24 hours.

TABLE I Example No 1266 1450 1450 1450 1450 1450 1450 1450 1450 13871450 1450 27-1 12-9 12-4 12-22 12-19 12-16 12-24 12-21 12-18 30-1 11-812-1 Compound 1 2 3 4 5 6 7 8 9 10 11 12 Polymer b- 100 100 100 100 100100 100 100 100 100 100 Crosslinking age C uinonedioxime dibenzoate Cuinonedioxime bis (p-mathoxyb enzoate) C uinonedioxime bis(p-chlorobenzoate) Cuinonedioxime distearate Qunonedioxime diheptanoataQunonedioxime dibuty'rate Quinonedioxime diaeetate Quinonedioxime bis(ehloroacetate) Lewis acid accelerator:

c Synergistic agent:

S arie acid Tribntyl citrate.- Tributyl borate Tributyl phosphatePercent gel of cured polymer at C 1 1 2 3 2 4 4 4 1 41 27 7 C 1 32 1 229 4 2 2 0 73 69 C. 0 73 78 2 60 77 3 55 73 54 77 73 200 C. 54 82 81 668 1 83 39 79 81 61 78 77 225 C 82 S6 85 79 78 82 73 83 81 86 79 ExampleNo 1387 1450 1450 1450 1450 1450 1450 1450 1450 1450 1450 1450 39-1611-9 12-6 12-11 12-7 12-2 12-13 12-10 12-5 1212 12-8 12-3 Compound 1 1814 15 16 17 18 29 10 21 22 23 24 Polymer b 100 100 100 100 100 100 100100 100 100 100 100 Crosslinklng ag dibenzoata bis (p-methoxyb enzoate)bis (p-chlorob enzoate) distearate diheptanoate dbutyrate diacetate acidaccelerator:

12 SDC14.5H1O

Fenic acetylaeetonate synergistic agent:

Stearic acid Trlbutyl citrate Tributyl boratc Tributyl phosphate Percentgel oi cured polymer at: 0

bis chloroacetate Table I Continued Example No 1387 1387 1387 1387 10071450 1007 1387 1387 1266 7-11 23-3 23-5 23-7 38-18 12-15 38-17 38-8 7-1531-3 Compound 25 26 27 28 29 30 31 32 33 34 e 35 olymer b- 100 100 100100 100 100 100 150 100 100 d 150 Crosslinking agen dibenzoatebis(pmethoxybenzoate) bis (p-chlorobenzoate) distearate diheptanoate...

Ferrie aeetylacetonate 1- synergistic agent: Ste i l Compound admixed ina Brabender Plastograph at Sil-110 C. for 5 minutes. hEthylene/propylene rubber (E.P.R.) containing 58;|=5 mole percentethylene. Mooney viscosity ML (212 F.) =42. e 15 minute curing time.E.P.R. percent gels measured after retluxing sample for 24 hours inn-heptane containing 0.3 weight percent, 2,6-diterd 100 partsethylene/propylene rubber containing 58:1;5 mole percent ethyleneadmired with 50 parts Sterling MT carbon black. 100 partsethylene/propyiene rubber containing 58:1:5 mole percent ethyleneadmired with 50 parts Spheron 9 carbon black.

As is readily seen in Table I, the addition of a Lewis icid acceleratorto the curing agent of this invention :auses curing `at a lowertemperature range than the :rosslinking agent per se; compare, e.g.compounds 1 md 2 or 4 and `5 and the like. In addition it is to be xotedthat the addition of a synergistic agent to the :ompound causes curingto occur at a still lower temperature than the combination of curingagent and ae- :elerator; compare, e.g. compounds 2 and 3. The addi- :ionof the synergistic agent to the curing agent with- )ut any acceleratorappears to give only a marginal irn- )rovement in lowering the curingtemperature; compare :ompounds 1 and 31. However, when the accelerator sadded to the curing system a substantial lowering )f the curingtemperature is obtained. This is readily ipparent from FIGURE I whichshows graphically the effect of a Lewis acid acceleartor i.e. ZnClZ anda synergistic agent i.e. tributyl citrate on a curing agent, quinonedioxine dibenzoate (DBGMF) for ethylene/ propylene rubber (EPR).

FIGURE II shows the accelerating effect of various Lewis acid:accelerators on the curing agent, quinone dioxime dibenzoate (DBGMF)for curing EPR in the presence of various synergistic agents. In allcases, euring occurred at a lower temperature in the presence of anaccelerator than occurs with solely a curing agent.

Table II shows a comparative study of the accelerating eiect of theLewis acid accelerators and synergistic agents on the crosslinking ofvarious polymers derived from aolens. The compounding was performedduring a 10 minute milling period in a Brabender Plastograph attemperatures ranging from 10-30 degrees centigrade above TAB L E IIExample No Ferrie acetylacetonate Fe C la iynerglstic agent:

Stearic acid Tributyl citrate erceut gel of cured polymer at: h

l Compound admired in a Brabender Plastograph for 5-10 minutes. Rubbersmilled at 80-110 C.; thermoplastic polymers milled at 15-25 C. above`heir melting point. b Polyethylene;

density 0.96 g./cc., melt index 0.7 and 137 C. melting point.

v Polypropylene; density 0.899 g./cc., melt index 4.4 and 172-173 C.melting point.

d Ethylene/butylene copolymer containing 1.0 weight percent butylene;density 0.93 g./cc l Chlorosulioneted polyethylene rubber, specificgravity L12-1.28, sold under trade name .Hypalon 20, E. I. du Pont &Co., Inc.

l Ethylenepropylsene/diene terpolymer rubber, specic gravity 0.85, soldunder the trade name ECD-330, E. I. du Pont a Co., Inc., Mooney vis-:osity ML (212 F 5. l Ethylene/vinyl acetate copolymer containing 72weight percent ethylene; density 0.95 g./cc. at 30 C., sold under thetrade name "Elvax 250, E. I.

lu Pont & Co., Inc., melt index 15.

h 15 minute curing period. Percent gel measured after reiiuxing weighedsample for 24 hours in xylene for polyethylene, polypropylene, ethylene]Jutylene copolymer and ethylene/vinyl acetate copolymer; in methyl ethylketone for chlorosultonated polyethylene and in n-heptane for ethylene]propylene/diene terpolymer. All retluxing solvents contain 0.3 weightpercent 2,6-d1tertiary-butyl-4-metl1y1 phenol.

the softening point of the thermoplastic polymers and at 80-110 Cf forthe rubbers. Samples of the polymers lwere shaped into 6" x 6" x 0.02"tensile plaques in a platen press for 1 minute at 12S-165 C., dependingon the softening point of the thermoplastic polymer, and atmosphericpressure, followed by a 2 minute press at 12S- 165 C. and 625 p.s.i.pressure. The samples were removed from the mold and cured in a platenpress for minutes at 625 p.s.i. and varying curing temperatures. Weighedsamples of the cured polymers derived from aolens were then measured forgel content in suitable reiluxing solvents containing a small amount ofan antioxidant for 24 hours. The rubbers in Table II were cured andmeasured for percent gel in the same manner as the EPR in Table I exceptthat for chlorosulfonated polyethylene the solvent used was methyl ethylketone.

The results in Table II show the operability of the Lewis acidaccelerators and the synergistic agents of this invention in loweringthe curing temperature of the curing agent for various polymers derivedfrom a-olens.

FIGURE III shows a comparison of the curing system of the instantinvention with the presently recommended commercial curing system forethylene/propylene rubber (EPR) for 15 minute curing periods. Thepresent commercially recommended curing system for EPR consistsessentially of dicumyl peroxide with a small amount of sulfur tominimize degradation during the cure. Zinc Oxide (ZnO) is added tocreate a neutral or basic environment for the dicumyl peroxide andcalcium stearate is added as a processing aid to prevent Scorch. FromFIGURE III it is readily seen that the curing system of the instantinvention causes curing to occur at a lower temperature and to a highdegree within the preferred curing temperature range of 13G-150 C` forEPR.

We claim:

1. A curable composition consisting essentially of 100 parts by weightof a polymeric material containing at least 50 mole percent of a polymerderived from an olen, said polymeric material being selected from thegroup consisting of polyethylene, polypropylene, ethylenebutylenecopolymer, chlorosulfonated polyethylene, ethylene, ethylene-vinylacetate copolymer and ethylene-propylenediene terpolymer, 0.1 to 30parts/ 100 parts of said polymeric material by Weight of a curing agentof the general formula:

wherein R is a member of the group consisting of benzoate and analiphatic acyloxy group containing 1 to 20 carbon atoms and 0.005 to 1.0part/ 100 parts of said polymeric material by weight of a Lewis acidselected from the group consisting of FeCl3, ferrie acetylacetonate,A1Cl3, [ZnClz] and SnCl4 5H2O.

2. A curable composition consisting essentially of 100 parts by weightof a polymeric material containing at least 50 mole percent of a polymerderived from an otolefn, said polymeric material being selected from thegroup consisting of polyethylene, polypropylene, chlorosulfonatedpolyethylene, ethylene-butylene copolymer, ethylene-vinyl acetatecopolymer and ethylene-propylenediene terpolymer, 0.1 to 30 parts/ 100parts of said polymeric material by weight of a curing agent of thegeneral formula:

wherein R is a member of the group consisting of benzoate and analiphatic acyloxy group containing 1 to 20 carbon atoms, 0.005 to 1.0part/ 100 parts of said polymeric material by weight of a Lewis acidselected from the group consisting of FeCl3, ferric acetylacetonate,AlCl3, ZNClZ and SnCl45H2O and 0.1-30 parts/100 parts by weight of saidpolymeric material of a synergistic agent for curing said polymericmaterial consisting of a polar organic member of the group consisting ofcarboxylic acid, phosphoric acid, boric acid and esters thereof.

3. The method of curing polymeric material containing at least 50 molepercent of a polymer derived from an a-olen, said polymeric Imaterialbeing selected from the group consisting of polyethylene, polypropylene,chlorosulfonated polyethylene, ethylene-butylene copolymer,ethylene-vinyl acetate copolymer and ethylene-propyIenediene terpolymercomprising mixing together parts by weight of said polymeric material,0.1 to 30 parts/ 100 parts of said polymeric material by weight of acuring agent of the general formula:

wherein R is a member of the group consisting of benzoate and analiphatic acyloxy group containing 1 to 20 carbon atoms and 0.005 to 1.0part/ 100 parts of said polymeric material by weight of a Lewis acidselected fro-m the group consisting of FeCl3, ferric acetylacetonate,A1Cl3, ,[ZnClg] and SnCl4-5H2O and thereafter heating the resultantmixture to effect curing of said polymeric material.

4. The method according to claim 3 wherein a synergistic agent forcuring said polymeric material consisting of a polar organic member ofthe group consisting of carboxylic acids, phosphoric acid, boric acidand esters thereof is added to the mixture prior to heating said mixtureto effect curing of said polymeric material.

5. The composition according to claim 1 in which the compositioncontains in addition, 0.05 to 200 parts/100 parts of said polymericmaterial by weight of a filter for said polymeric material.

6. The composition according to claim 5 wherein the liller is carbonblack.

7. The method according to claim 3 wherein 0.05 to 200 parts/ 100 partsof said polymeric material by weight of a filler for said polymericmaterial is added to the mixture prior to heating said mixture to efrectcuring of the polymeric material.

8. The method according to claim 7 wherein the liller is carbon black.

9. The composition according to claim 1 wherein.' the Lewis acid isFeCl3.

10. The composition according to claim 1 wherein the Lewis acid isferrie acetylacetonate.

1]. The composition according to claim 1 wherein the Lewis acid isAlClS.

12. The composition according to claim 1 wherein the Lewis acid isSnCl4-5H2O.

13. The method according to claim 3 wherein the Lewis acid is FeCl3.

14. T he method according to claim` 3 wherein the Lewis acid is ferrz'cacetylacetonate.

15. The method according to claim 3 wherein the Lewis acid is AlCl.

16. The method according to claim 3 wherein the Lewis acid isSnCl4-5H20.

References Cited The following references, cited by the Examiner, are ofrecord in the patented tile of this patent or the original patent.

UNITED STATES PATENTS 2,748,104 5/1956 Viohl 260-41 3,012,020 12/1961Kirk et al. 260-41 3,093,614 6/1963 Mackenzie et a1. 260-41 OTHERREFERENCES Morton: Introduction to :Rubber Technology, Reinhold, NewYork, 1959, pp. 323-324.

ALLAN LIEBERMAN, Primary Examiner U.S. C1. X.R.

